Intravenous iodinated contrast agents are generally safe. Though the frequency of side effects has fallen significantly since the introduction of nonionic, monomeric contrast agents,1 however, side effects remain an important issue.2 Late adverse reactions were first recognized in the mid-1980s.3 Many aspects of these reactions remain controversial, and uncertainty is widespread among radiologists about their incidence, significance, and management.
To shed some light on the topic, we conducted a questionnaire study of patients undergoing CT scans. We addressed the common delayed side effects following administration of iodinated contrast media and considered the current literature.
The prospective questionnaire study was carried out during 2005 and 2006 among 800 patients attending Belfast City Hospital’s radiology department for a CT scan of the abdomen. A total of 600 patients received both IV and oral contrast; of these, 200 patients received nonionic dimeric iodixanol, another 200 were injected with nonionic monomeric iohexol, and the remaining 200 were administered nonionic monomeric iomeprol. The other 200 patients received only oral contrast and served as the control group.
Patients stayed in the department for one hour after the injection. Staff gave them a questionnaire following the scan and asked them to return it in a prepaid envelope after one week. The questionnaire was in a simple format, with mostly “yes” or “no” answers. Patients were asked to document immediate and delayed reactions. Immediate reactions were defined as those occurring within the department and delayed as those occurring between the time the patients left the department and up to seven days later.
The delayed side effects were divided into three main categories: skin, gastrointestinal, and general reactions. Skin effects included itching, rash, and hives. Nausea, vomiting, and diarrhea were the gastrointestinal side effects, and general side effects included headache, dizziness, and fever. Patients were also asked to provide information about any history of asthma, any previous reaction to medication, whether they were receiving steroids or chemotherapy, and if they required medical help because of the side effect (see table).
A total of 562 (70.25%) patients returned the questionnaire. Of these, 445 (79.18%) had received IV contrast and 117 (20.82%) were from the control group. There were 206 men and 239 women who received IV contrast and 46 men and 71 women in the control group. Among the group receiving IV contrast, 140, 155, and 150 patients had received iohexol, iomeprol, and iodixanol, respectively.